Segment information - Schedule of Significant Expense Categories Within Net Loss (Details) - USD ($) $ in Thousands |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2025 |
Jun. 30, 2024 |
Jun. 30, 2025 |
Jun. 30, 2024 |
|
| Segment Reporting Information [Line Items] | ||||
| Research and development | $ 42,760 | $ 32,514 | $ 86,404 | $ 62,445 |
| Tarcocimab Program Expenses | ||||
| Segment Reporting Information [Line Items] | ||||
| Research and development | 11,886 | 9,157 | 26,162 | 15,126 |
| KSI-501 AndKS I-101 Program Expenses | ||||
| Segment Reporting Information [Line Items] | ||||
| Research and development | 5,309 | 1,080 | 9,526 | 3,301 |
| ABC Platform And Other Program Expenses | ||||
| Segment Reporting Information [Line Items] | ||||
| Research and development | 6,421 | 3,115 | 12,066 | 5,701 |
| Payroll And Personnel Expenses | ||||
| Segment Reporting Information [Line Items] | ||||
| Research and development | 14,109 | 14,492 | 28,379 | 28,851 |
| Facilities And Other Research And Development Expenses | ||||
| Segment Reporting Information [Line Items] | ||||
| Research and development | $ 5,035 | $ 4,670 | $ 10,271 | $ 9,466 |